Green Turtle

Species Description

The ‘vonu dina’ is the largest of all the hard-shelled sea turtles. While hatchlings are just 2 inches (50mm) long, adults can grow to more than 0.9m long and weigh 130-160kg.

Adult green turtles are unique among sea turtles in that they are herbivorous, feeding primarily on sea grass and algae. This diet is thought to give them greenish coloured fat, from which they take their name. A green turtle’s carapace (top shell) is smooth and can be shades of black, grey, green, brown and yellow while their bottom shell is yellowish white.

Like most other turtles, the ‘vonu dina’ reaches sexual maturity between 30 to 45 years, at which time females begin to leave their foraging or feeding grounds and return to their nesting grounds after every 2 to 4 years. The nesting season varies depending on location. In Australia and Papua New Guinea, which are the main nesting grounds, females generally nest between the months of June to August. Due to variations on climatic conditions, nesting seasons in Fiji may differ by one or two months favoring the period of August and September. During the nesting season, females nest at approximately two week intervals, laying an average of five clutches.

Habitat

Scientists say that green turtles primarily use three types of habitat: oceanic beaches (for nesting), convergence zones in the open ocean, and benthic feeding grounds in coastal areas. Adult females will migrate from their feeding grounds to their mainland or island nesting beaches and in doing so, may travel hundreds or thousands of kilometres each way. After emerging from the nest, hatchlings swim to offshore areas, where they are believed to live for several years, feeding close to the surface on a variety of pelagic plants and animals. Once the juveniles reach a certain age/size range, they leave the pelagic habitat and travel to nearshore feeding grounds. Once they move to these nearshore benthic habitats, adult green turtles are almost exclusively herbivores, feeding on sea grasses and algae.

Distribution

The green turtle is globally distributed and generally found in tropical and subtropical waters along continental coasts and islands. Nesting occurs in over 80 countries throughout the year (though not throughout the year at each specific location). Green turtles are thought to inhabit coastal areas of more than 140 countries. In Fiji, Green turtles are usually found at the Heemskerq and Ringgold reefs.

Population Trends

In 2004 the World Conservation Union (IUCN) classified green turtles as endangered globally. Analyses of historic and recent abundance information by the IUCN indicates that extensive population declines have occurred in all major ocean basins over approximately the past 100 to 150 years. An estimate of only about 203,000 nesting females is said to be surviving on the global scale, with Fiji less than 100 females estimated to be left in Fiji waters.

Threats

As in the case of all marine turtles, the principal cause of the historical, worldwide decline of the green turtle is long term harvest of eggs and adults on nesting beaches and juveniles and adults on feeding grounds. These harvests continue in some areas of the world including Fiji and compromise efforts to recover this species. Incidental capture in fishing gear, primarily in gillnets, but also in traps and long-lines is a serious ongoing source of death that also adversely affects the species’ recovery. Green turtles are also threatened, in some areas of the world, by a disease known as fibropapillomatosis (FP).

Conservation Efforts

Green turtles are protected by various international treaties and agreements as well as national laws. Green turtles are listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES), which means that international trade of this species is prohibited. Green turtles are listed in Appendices I and II of the Convention on Migratory Species (CMS) and are protected under the following instruments of CMS: the Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and South-East Asia (IOSEA) and the Memorandum of Understanding Concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa.